Advanced Heat Transfer: Thermal Radiation

Thermal Radiation, Blackbody, Kirchhoff, Plank and Wien’s displacement Laws, View Factor, Radiation Exchange and more

We start this course with a discussion of electromagnetic waves and the electromagnetic spectrum, with particular emphasis on thermal radiation. Then we introduce the idealized blackbody, blackbody radiation, and blackbody radiation function, together with the Stefan–Boltzmann law, Planck’s law, and Wien’s displacement law.

What you’ll learn

  • Classify electromagnetic radiation, and identify thermal radiation.
  • Understand the idealized blackbody, and calculate the total and spectral blackbody emissive power.
  • Calculate the fraction of radiation emitted in a specified wavelength band using the blackbody radiation functions.
  • Understand the concept of radiation intensity, and define spectral directional quantities using intensity.
  • Develop a clear understanding of the properties emissivity, absorptivity, relflectivity, and transmissivity on spectral, directional, and total basis.
  • Apply Kirchhoff’s law to determine the absorptivity of a surface when its emissivity is known.
  • Define view factor, and understand its importance in radiation heat transfer calculations.
  • Develop view factor relations, and calculate the unknown view factors in an enclosure by using these relations.
  • Calculate radiation heat transfer between black surfaces.
  • Determine radiation heat transfer between diffuse and gray surfaces in an enclosure using the concept of radiosity.
  • Quantify the effect of radiation shields on the reduction of radiation heat transfer between two surfaces.

Course Content

  • Fundamentals of Thermal Radiation –> 23 lectures • 4hr 44min.
  • Radiation Exchange Between Surfaces –> 22 lectures • 2hr 49min.
  • Exercise Files –> 1 lecture • 1min.

Advanced Heat Transfer: Thermal Radiation

Requirements

  • Fundamentals of Heat Transfer Course.
  • Engineering Thermodynamics Course.

We start this course with a discussion of electromagnetic waves and the electromagnetic spectrum, with particular emphasis on thermal radiation. Then we introduce the idealized blackbody, blackbody radiation, and blackbody radiation function, together with the Stefan–Boltzmann law, Planck’s law, and Wien’s displacement law.

Radiation is emitted by every point on a plane surface in all directions into the hemisphere above the surface. The quantity that describes the magnitude of radiation emitted or incident in a specified direction in space is the radiation intensity. Various radiation fluxes such as emissive power, irradiation, and radiosity are expressed in terms of intensity. This is followed by a discussion of radiative properties of materials such as emissivity, absorptivity, reflectivity, and transmissivity and their dependence on wavelength, direction, and temperature. The greenhouse effect is presented as an example of the consequences of the wavelength dependence of radiation properties.

We then discuss view factors and the rules associated with them. View factor expressions and charts for some common configurations are given, and the crossed-strings method is presented. We then discuss radiation heat transfer, first between black surfaces and then between nonblack surfaces using the radiation network approach. We continue with radiation shields and discuss the its radiation effects.